Inhibition of breast and ovarian carcinoma cell growth by 1,25-dihydroxyvitamin D3 combined with retinoic acid or dexamethasone.

This study examined the growth inhibitory effects of combining 1,25-dihydroxyvitamin D3 (calcitriol) with retinoic acid or dexamethasone against cultured breast and ovarian carcinoma cells. Retinoic acid (12.5-50 nM) increased the effectiveness of calcitriol (12.5-50 nM) against MCF-7 and NIH:OVCAR3 cells, with synergistic interactions at two of the three ratios tested. Dexamethasone augmented calcitriol effects, with synergism at 0.05 and 0.1 nM dexamethasone in MCF-7 cells and 5 nM in Caov-4 ovarian cells. This study showed favorable interactions for calcitriol-retinoic acid and calcitriol-dexamethasone combinations in breast and ovarian cancer cell lines.